Notes on Robotic Total Knee Replacement

  • Term ‘robot’ originates from the Czech word ‘robota’, which means forced labour or activity.
  • Karel Capek first used the term ‘Robot’ in his 1921 play called Rossum’s Universal Robots.
  • Robots are defined as an array of computer controlled machines that perform preprogrammed, precise, and repetitive procedures.
  • Robotic technology allow to sustain levels of precision, productivity, and efficiency that were not possible with humans alone.
  • First robotic surgical procedure was performed by Kwoh  in 1988 using the PUMA 560 robotic system (Westinghouse Electric, Pittsburgh, Pennsylvania) to undertake neurosurgical biopsies with improved precision.
  • Advantages of robotic surgery
    • Smaller skin incisions
    • Improved precision of soft-tissue dissection
    • Better visualisation of the surgical field
    • Comprehensive data capture for surgical training
    • Early recovery
    • Shorter hospital stay
  • Disadvantages
    • Expensive to install
    • Needs separate applications for total hip arthroplasty, TKA, and unicompartmental knee arthroplasty.
    • Compatible with a limited number of implants from the manufacturer of the robotic device
    • Additional costs are incurred for preoperative imaging
    • Radiation exposure for CT
    • Increased operating times during the learning phase
    • Needs training the surgical team
    • Updating of computer software needed
    • Needs servicing contracts and consumables.
    • Additional time needed for planning and modelling
    • Product specialists needed in the OT
    • Technical issues with robot arm may need intra-operative conversion to conventional jigs
    • Maintenance costs
    • Paucity of long-term data showing any functional benefit

Why consider robots for TKR?

  • Up to 20% of patients remaining dissatisfied following TKA.
  • Surgeon controlled variables affecting outcome in TKR
    • Accurate implant positioning
    • Balanced flexion-extension gaps
    • Proper ligament tensioning
    • Preservation of periarticular soft-tissue envelope
  • Conventional jig-based TKA uses preoperative radiographic films, intra-operative anatomical landmarks, and manually positioned alignment jigs to guide bone resection and implant positioning.
  • Conventional jig-based TKA is associated with poor reproducibility of alignment-guide positioning, inadvertent saw blade injury to the periarticular soft-tissue envelope, and limited intra-operative data on gap measurements or ligamentous tensioning to fine tune the implant positioning.
  • Suboptimal implant positioning may lead to
    • Poor functional recovery
    • Reduced clinical outcomes
    • Increased instability
    • Reduced implant survivorship
  • In navigated TKR, computer software converts anatomical information obtained from preoperative CT or intra-operative osseous mapping into a virtual patient-specific 3D model of the knee joint.
  • Virtual model is used to plan optimal bone resection, implant positioning, bone coverage, and limb alignment based on the patient’s unique anatomy.
  • Computer navigated TKA provides patient-specific anatomical data with recommendations for bone resection and optimal component positioning.
  • In robotic TKR, a robotic device helps to execute this preoperative patient-specific plan with a high level of accuracy.
  • Robotic TKR uses optical motion capture technology to assess intra-operative alignment, component positioning, range of movement, flexion-extension gaps, and soft tissue balancing.
  • RTKR actively controls and/or restrains the surgeon’s motor function to improve the accuracy of achieving the planned bone resection and implant positioning.
  • Real-time intra-operative data can then be used to fine-tune bone resection and guide implant positioning, in order to achieve the desired knee kinematics and limit the need for additional soft-tissue releases.
  • First robotic TKA was performed in 1988 using the ACROBOT robotic system (Imperial College, London, United Kingdom).


  • Classified into
    • Imageless or Image guided
    • Fully-active or semi-active
  • Fully active is actively involved in all steps of bone resection and soft tissue balancing.
  • Semi-active provides the surgeon with visual, tactile, and audio feedback that provides stereotactic boundaries that confines the saw blade to pre-planned haptic femoral and tibial windows to achieve accurate bone resection and soft tissue balancing.
  • RTKR associated with improved accuracy of achieving the planned femoral and tibial implant positioning, joint line restoration, limb alignment, and posterior tibial slope compared with conventional jig-based TKA.
  • Results in improved accuracy in implant positioning in all three planes and reduces outliers.
  • RTKR associated with learning curve of six to 20 cases for operative times, but there is no learning curve for achieving the planned femoral or tibial implant positioning. This allows even low volume surgeons to improve accuracy.
  • Improved accuracy of implant positioning and enhanced postoperative rehabilitation in robotic TKA have not translated to any differences in middle- to long-term functional outcomes compared with conventional TKA.
  • There is a paucity of prospective randomized controlled trials reporting on longer-term outcomes.

Based on the Open access article published in Bone and Joint Research

Robotic total knee arthroplasty clinical outcomes and directions for future research by Babar Kayani & Fares S Haddad.

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